Firs my credentials, so to speak: I've been playing FF14 since the A Realm Reborn patch days. Sometime around 2.1 or 2.2. I am a casual player. I have never once raided, even unsynched. I don't have the time or inclination to do it. The most difficult content I've ever done are alliance raids and a few EX trials (although the vast, vast majority of my mounts come from grinding them unsynched). I cannot speak to how Kaiten works/ed in top tier end game content, and, frankly, other people have already done so quite eloquently.
I am also a physically disabled gamer. I was born with a condition called Arthrogryposis Multiplex Congenita. It's essentially a form of MD. I've had over 40 surgeries to give me what little function I currently enjoy. Because of this, I cannot use keyboard an mouse controls (no, not even with a MMO mouse... I've tried), and must instead use a controller to play.
So, with that out of the way let me say this: button bloat IS a real thing. It's not an inconvenience, but an accessibility issue. However, Kaiten WAS NOT a main contributor to button bloat, and there are plenty of other ways to reduce the number of buttons on Samurai, such as making Ikishoten -> Ogi Namikiri -> Kaeshi: Namikiri a single button that changes (like Gunbreaker's Continuation combo) or even Iaijutsu -> Tsubame-Gaeshi on a single button.
I understand why the devs removed Kaiten... it's not really different than the old Heavensward DRK Dark Arts spam. But as that job never fully recovered from DA's removal in terms of feel and flow and soul (IMO), so too will Samurai suffer from losing Kaiten. Not necessarily because of job performance number-wise (although, there's a case for that, too), but rather because of it's feel and flow and soul.
I'd much rather that the devs create a ton of different jobs that run the gamut between exceptionally easy/basic and skillful than attempt to narrow the bandwidth (for lack of a better term) between them all. And Samurai was skillful without being too difficult. Easy to learn, but it took some effort to master. Which made it fun. Please, devs, with all due respect for making this marvelous, physically accessible game that even people like me can play, roll back the Kaiten change.
Thank you for reading